This invention relates to repairing cartilage, for example, articular cartilage on the femur.
Articular cartilage that is damaged (e.g., torn or excessively worn) may be repaired in a variety of ways. For example, the damaged cartilage may be shaved or scraped from the bone surface, thereby causing bleeding which stimulates the growth of fibrocartilage. Small holes may be drilled in the bone to promote bleeding and fibrocartilage growth. Alternatively, an allograft (e.g., cartilage grown in vitro from cartilage tissue removed from the patient) may be implanted by attaching a periosteum membrane (harvested, e.g., from the patient""s tibia) to the bone surface and injecting the allograft beneath the membrane. The periosteum provides a healthy environment which promotes further cartilage cell growth.
This invention features, in general, a method of repairing cartilagexe2x80x94and a set of instruments used in the methodxe2x80x94by removing the damaged cartilage from the bone to expose the underlying bone, harvesting grafts covered with cartilage from elsewhere in the body, and inserting the grafts into holes drilled into the exposed area of bone. The invention is particularly useful (but by no means exclusively so) in repairing damaged articular cartilage on the femur with bone grafts covered with hyaline cartilage that are harvested from another area of the femur.
One general aspect of the invention features a guide for use with surgical instruments during the procedure to orient the surgical instruments perpendicularly to the bone surface during use. The guide includes a guiding portion disposed along a longitudinal axis for engaging the surgical instrument, and a tissue-engaging portion oriented perpendicularly to the longitudinal axis.
Preferred embodiments may include one or more of the following features.
The surgical instruments used with the guide include a drill for drilling a hole for receiving the tissue graft, a dilator having a distal end sized to enlarge the hole, and an insertion tool for inserting the tissue graft into the hole. The guiding portion of the guide is sized to receive each instrument and orient it perpendicularly to the bone surface. Preferably, the tissue graft includes bone with a layer of cartilage thereon.
Preferably, the drill includes a distal end that comprises a pointed distal tip and a plurality of cutting flutes circumferentially spaced around the distal end proximally adjacent to the tip. The drill includes markings to indicate a depth of the hole. The distal end of the dilator is preferably tapered, and the dilator includes markings to indicate the depth that the distal end is inserted in the hole.
The portion of the insertion tool engaged by the guide has an adjustable length relative to the length of the guide so that the amount by which the graft protrudes from the hole can be correspondingly adjusted. The length-adjustable portion of the insertion tool includes a rod attached to a handle configured to engage a proximal end of the guide. The distal end of the rod is configured to engage the graft, and the proximal end of the rod is progressively insertable into an opening in the handle to adjust the length of the rod.
For example, the proximal end of the rod is threadably received within the opening so that relative rotation between the handle and the rod adjusts the length of the rod. A resilient member disposed in the opening engages the proximal end of the rod to maintain the rod in position at the adjusted length. The rod includes markings to indicate the amount by which the graft protrudes from the hole.
The guide may have a wide variety of suitable configurations. Preferably, the guide comprises a tube having a passage disposed along the longitudinal axis to provide the guiding portion. The tissue-engaging portion is disposed at a distal end of the tube and is, for example, a rim of the tube. In some embodiments, the tissue-engaging portion also includes an annular flange that projects distally from the rim and is configured to be seated within the bone tissue. In other embodiments, the tissue-engaging portion comprises an enlarged lip disposed circumferentially around the distal end of the tube. A portion of the lip may include a recess therein.
The guide may also include a spacer for positioning the guiding portion at a selected location relative to a feature on the bone tissue. For example, the feature is a hole in the bone tissue. In this case, the spacer includes a member (e.g., a pin or a tooth) that projects distally from the tissue-engaging portion of the guide for insertion into the hole. The member may be retractable with respect to the tissue-engaging portion, or not. The member may be disposed on a sleeve that is insertable over the guide. If the feature includes a region of cartilage on the bone tissue, the spacer may include an enlarged lip disposed adjacent to the tissue-engaging portion of the guide for engaging the region of cartilage.
In some embodiments, the guide includes a window for allowing viewing of the passage. The guide may include a valve for blocking fluid flow through the passage. In other embodiments, a portion of the guide comprises clear material.
Another aspect of the invention features a set of instruments that includes the guide, the drill, and the insertion tool.
In preferred embodiments, these instruments are sized to insert a tissue graft having a selected size. At least one other set of such instruments may be provided and sized to insert tissue grafts of a different size.
The set of instruments may also include the dilator and a template for measuring a size of the tissue graft.
In addition, the set may include a tool for removing the tissue graft from a bone. The tool includes a chisel having a hollow shaft that extends distally from a handle and terminates in a sharpened, hollow tip configured to capture the tissue graft therein, the handle having a passage therein that communicates with the hollow shaft. A collar is slidable over the shaft to shield the hollow tip during removal of the tissue graft therefrom, and a member is insertable into the hollow tip to engage the tissue graft and remove the tissue graft proximally through the shaft and the passage of the handle. The collar includes a flared opening disposed adjacent to the tip when the collar is inserted over the shaft. The member applies force to the bone portion of the graftxe2x80x94rather than the cartilage on the upper surface of the graftxe2x80x94during removal, thereby reducing the risk of damaging the cartilage.
The set of instruments may also be equipped with a device for determining an entry portal for the guide over the bone surface. The device includes a needle disposed along a longitudinal axis and having an open distal end, and a plurality of prongs disposed within said needle and having resiliently curved distal tips. The prongs are slidable within the needle between a retracted position in which the distal tips are disposed within the needle and an extended position in which the distal tips project from the needle to engage the bone surface and define a plane that is perpendicular to the longitudinal axis. The device is small and can be inserted into the body even multiple times to determine the correct (e.g., perpendicular) entry portal location with a minimum of patient trauma.
Another general aspect of the invention features a method of inserting a tissue graft using the instruments discussed above.
Among other advantages, the invention provides an efficient and accurate way of repairing cartilage that may be performed arthroscopically, thereby reducing trauma and minimizing healing time. The guide allows the graft-receiving holes to formed perpendicularly to the bone surface and the graft to be inserted straight into the hole, despite the curved nature of the bone. This greatly enhances the match between the grafted cartilage and the contour of the surrounding cartilage. In addition, because the height of the graft (i.e., the amount that the graft protrudes from the hole) is adjustable, the grafted cartilage can be easily positioned at the same height as the surrounding cartilage. This provides a high quality repair and reduces the risk that further surgery will be needed to sculpt the grafted cartilage to the height and contour of the surrounding, existing cartilage.
In addition, the various configurations of the guide allow the graft receiving holes to be marked and closely positioned with respect to each other while maintaining sufficient bone wall thickness to promote healing and a healthy environment for the grafts. The accessories provided with the chisel (e.g., the collar and graft-removal member) greatly facilitate withdrawal of the graft from the chisel without injuring the surgeon (with the sharp chisel tip) or damaging the graft (with the graft-removal member). The entry portal positioning device allows the surgeon to determine the correct (e.g., perpendicular) entry portal location with a minimum of patient trauma.
Other features and advantages of the invention will become apparent from the following detailed description, and from the claims.